The present application relates to a gas pressure control valve for receiving gas from a high pressure source and supplying the gas at a low pressure to a user. More particularly embodiments of the present invention concern a compact gas pressure control valve for regulating gas pressures from low capacity gas capsules (e.g. a water capacity of 5 to 100 ml with a typical commercial size being 21 ml).
Typically gas is stored within gas cylinders at high pressures (e.g. 200 bar). However, often in use much lower pressures are required. It is therefore necessary to provide a gas pressure control valve which can regulate the pressure of gases. In addition to providing a means to provide gas at a lower pressure to a user, gas pressure control valves also enable the pressure of gas to be controlled and maintained at a relatively constant rate which does not differ significantly whether a gas cylinder is empty or full.
Examples of prior gas pressure control valves are disclosed in U.S. Pat. No. 4,655,246 and U.S. Pat. No. 5,307,834.
Although prior valves do enable gas pressure to be regulated, existing designs are used in the context of regulating gas pressure from large gas cylinders. It would be desirable to be able to provide a gas pressure control valve which is suitable to regulate gas pressure from smaller capacity gas capsules. However, reducing the size of existing designs is difficult because the designs are sensitive to certain design parameters. Adapting existing designs for use with smaller gas cylinders is therefore difficult as such smaller valves would be unreliable unless they were to be manufactured to excessively high manufacturing tolerances. In particular it is difficult to make the high pressure sealing seat small enough to allow a very small piston, and still maintain pressure control over the range of pressures from the cylinder. As a consequence, conventional valves are not used with small capacity gas capsules and the gas flow from such capsules has not been regulated. This has limited the use of such capsules to applications where high pressure gas supply is required or alternatively applications such as the supply of liquefied gases where pressure is lower and constant as it is effectively controlled by the vapor pressure of the liquid.
An alternative design of gas pressure control valve which is suitable for use with low capacity gas capsules is therefore desired.